Under barbiturate anesthesia, microelectrode recordings from the trigeminal ganglion of monkey are performed and electrical activity is recorded and stored on magnetic tape. Thermal and noxious heat stimuli are delivered with a precisely-controlled thermode which has a temperature range of 20 degrees C to 60 degrees C and can produce a temperature change of 10 degrees C at the thermode-skin junction within one second. Data is analyzed with the aid of an on-line, real-time computer system. BIBLIOGRAPHIC REFERENCES: Beitel, R.E. and Dubner, R.: Fatigue and adaptation in unmyelinated (C) polymodal nociceptors to mechanical and thermal stimuli applied to the monkey's face. Brain Research 112:402-406, 1976. Beitel, R.E. and Dubner, R.: Sensitization and depression of C polymodal nociceptors by noxious heat applied to the monkey's face. In: J.J. Bonica and D. Albe-Fessard (Eds) Advances in Pain Research and Therapy, Raven Press, New York, 1976, p. 149-153.